The present invention is related generally to enclosures for printed circuit boards.
The proliferation of printed circuit boards is electrical devices has resulted in the availability of a wide variety of enclosures for printed circuit boards. Since printed circuit boards are often used in mass produced consumer goods such as clocks, radios, etc., it is extremely important to have an enclosure which is both easy to assemble and inexpensive as well as providing adequate physical protection and separation between plural boards and the housing and other necessary functional features. The present invention is for such an enclosure.
There are currently a wide variety of enclosures for printed circuit boards known in the art. Such enclosures may be passive, i.e., merely holding the circuit board in the proper position, or active, i.e., providing electrical connections with the circuit board in addition to holding the circuit board in the proper position. A typical passive enclosure is shown in FIG. 1.
In FIG. 1 an enclosure has a front housing member 10 and rear housing member 12 each provided with integrally molded bosses 11. The front housing member and the rear housing member are typically held together by a screw, not shown. A front panel 14 may be integrally molded with the front housing member 10 or may be a separate member held in place by a screw 16 as is commonly provided when the front panel 14 carries control switches or the like. Printed circuit boards 17 are typically held in place by the combination of tubular spacers 18 and a screw 20 extended through holes in the circuit boards 17. The enclosure shown in FIG. 1 is particularly advantageous when it is necessary to service the printed circuit boards 17. By removing the screw holding the rear housing member 12 to the front housing member 10, the planar surface of the circuit board 17 is exposed.
However, the tubular spacers 18 require valuable space on the surface of the circuit boards which could otherwise be used for electrical components. Additionally, production errors in locating the hole for the screw 20 in the circuit boards 17 and assembly errors in lining up the tubular spacers 18 are cumulative. It is also possible to use the wrong length of spacer between given boards and/or the housing so a to result in improper spacing. This arrangement also requires a relatively large number of manual assembly steps. Thus, the enclosure shown in FIG. 1 is not well suited for accurately mounting a large number of printed circuit boards.
A second type of prior art enclosure is illustrated in FIG. 2. In FIG. 2, a central housing portion 22 is provided with pairs of opposing grooves 23 for holding the printed circuit boards. The central housing portion 22 may be integrally molded or molded in several pieces which are subsequently connected. The enclosure has a rear housing member 24 which may be intergrally molded with the central housing portion 22 or connected thereto by screws 25 or the like. The enclosure is completed by a front housing member 27 which is typically connected by screws, not shown. The enclosure illustrated in FIG. 2 may be an active enclosure by providing appropriate connectors in the rear housing member 24 adapted to receive edge connectors on the circuit boards.
Although the enclosure illustrated in FIG. 2 is well suited for holding a plurality of printed circuit boards and requires a minimum of surface area, it is not particularly well suited in applications where it is desirable to remove one of the housing members to expose the planar surface of the circuit board for servicing.